Method and device for reinforcing crankshafts

ABSTRACT

The present invention relates to a device and a method for surface rolling crankshafts at the transition radii of bearing journals. The method for surface rolling the transition radii of crankshafts comprises the following steps: providing at least one roller element for applying at least one force to the workpiece; providing at least one support element for supporting the workpiece against a force applied by a roller element; displacing the at least one roller element and/or the at least one support element such that the at least one support element, and the at least one roller element, perform a displacement relative to each other, the displacement having a linear component. The present invention further provides a roller element for surface rolling the transition radii of crankshafts having a substantially linear contact surface for introducing at least one surface rolling force into a crankshaft, and a corresponding device.

The present invention relates to a method and an apparatus for roll-solidifying of crankshafts at the transition radiuses of journals according to the preamble of claims 1 and 8. Such a method and apparatus is known from EP-B-213 256.

Roll-solidifying is a method for hardening surface layers by mechanical means. The effect of roll-solidifying is particularly based on the internal compression tensions that are introduced into the machined work piece, on an increase in strength that is achieved by forming, as well as on the provision of smoothening of the surface and removing of micro-notches. Particularly the combination of said three physical effects makes roll-solidifying effective.

During roll-solidifying, a defined and, if applicable, a variable roll-solidifying force is introduced via roller elements for roll-solidifying into the work piece to be machined, said roller elements for roll-solidifying form part of a roll-solidifying device. For introducing the force into the work piece, the roller elements for roll-solidifying roll on the rotating work piece.

Preferably, roll-solidifying is performed within the elastic range of the Young curve. Particularly preferred, roll-solidifying is performed by repeatedly performing single roll-solidifying actions. Roll-solidifying has proven to be advantageous over surface treatments by, for example, thermal treatment or laser treatment. Thus, roll-solidifying results in a considerably higher fatigue strength of the machined work pieces vis-à-vis conventional surface treatments and additionally results in an improved torsion strength which cannot or can only be insufficiently achieved by conventional surface treatments.

By roll-solidifying, material fatigue caused by cyclically increasing or changing mechanical stresses, a notch effect at variation of cross-section, sharp-edged transitions and working grooves, a notch effect due to internal tensions from the manufacturing process and tension jumps due to the introduction of outer forces, can be avoided. Such problems can occur in a plurality of technical devices as in, for example, devices of the general engineering, engines, transmissions, machine and road vehicles, water- and aircrafts etc. Roll-solidifying is particularly used for hardening of surface layers of critical areas of crankshafts, as, e.g., used in the automotive field.

Thus, roll-solidifying presents a manufacturing technology for improving the operation strength of highly stressed crankshafts. Here, it particularly serves the improving of the stability of crankshafts which thus can be used in, for example, power enhanced engines.

Crankshafts having an improved operability also allow the construction of more compact engines having a higher performance density. By roll-solidifying, particularly internal compression tensions are introduced into the chamfers of crankshafts, said internal compression tensions preferably result in an increase in the endurance limit of crankshafts and thus to a significant increase in life cycle.

Respective methods as well as apparatuses for performing such methods are known in the state of the art.

Thus, DE-C-30 37 688 relates to a method for roll-solidifying crankshafts at the transition radiuses of journals wherein roll-solidifying is performed over a rotational angle of the work piece of 360° and with different rolling forces. For this purpose, roller elements for roll-solidifying are used which supports against the chamfers of the crank journals on the one hand and, on the other hand, each in the running grooves of one race, which are supported by bolts via rolling bearings.

EP-B-0 215 179 relates to roll-solidifying apparatus or smooth rolling apparatus for rolling at least the surfaces arranged eccentrically at the work piece. The apparatus comprises roller-shaped support elements and roller elements which roll on the work piece in order to apply the forces.

EP-B-0 213 526 relates to a means for roll-solidifying or smooth rolling of crankshafts having at least one movable rolling device each of which comprises a tool carrier with at least one roller element and a toll carrier with at least one support element, as well as at least one further rolling device wherein the rolling devices are carried by a rack which can be arranged on a slide. The roller elements and support elements according to EP-B-0 213 256 are roller-shaped.

According to the methods known in the art, a roll-solidifying unit is formed by two roller-shaped roller elements with one support roller. This means, two roller elements which roll on the work piece and which introduce forces into said work piece are commonly supported by one support roller over which the roller forces are introduced into the roller elements. In this connection, it proves to be particularly disadvantageous that, e.g., the wear of only one roller element results in a respective wear of the support roller so that the replacement of the entire unit becomes necessary.

Additionally, inaccuracies in the work piece lead to imbalances in the forces within the roll-solidifying unit, since the roller force moments are introduced over both roller elements into the support roller. Such inaccuracies lead, for example, to a high force which is introduced over one solidifying roller into the support roller while the second solidifying roller only introduces a lower force at a different location into the support roller. Such a different load of the support roller requires high balancing forces: Said balancing force in turn increases the wear and reduces the life time of the roll-solidifying unit.

Particularly, there is the danger that damaging of one solidifying roller results in a standstill or blocking of a roll-solidifying unit. Additional, there is the danger that, due to the rotation-symmetric configuration of the solidifying roller, a damaged part of said roller comes repeatedly into contact with the crankshaft to be worked. This leads to a continuous, repeatedly applied damaged region on the crank shaft. Due to such damages of the solidifying roller or solidifying rollers there is the danger that no internal compression tensions are introduced into the crankshaft, as described above, or that already introduced internal tensions are removed. Additionally, there is the potential damaging of the work piece.

Furthermore, the instant when the wear of a solidifying roller exceeds a critical level, cannot be sufficiently detected during the operation of the unit.

A satisfactory and reliable working of crankshafts according to the methods known in the state of the art is not or not sufficiently possible. This is particularly true in view of the high costs which are caused by the described defects in mass production of crankshafts in the automotive field.

It is thus an object of the present invention to overcome the disadvantages of the state of the art. Particularly, it is an object of the present invention to provide an improved roller element, an improved apparatus as well as an improved method for roll-solidifying the transition radiuses of crankshafts.

The object(s) of the present inventions is(are) achieved by the roller element, the apparatus as well as the method according to the claims.

The present invention relates to a method for roll-solidifying the transition radiuses of crankshafts according to claim 1. Here, at least one roller element for introducing at least one force into the work piece as well as at least one support element for supporting the work piece against a roll-solidifying force introduced by the roller element are provided. Furthermore, the at least one roller element and/or the at least one support element are moved in such a manner that the work piece arranged between them and the at least one roller element perform a movement relative to each other, said movement comprising a linear component. Preferably, the relative movement between the work piece and the at least one roller element essentially comprises a linear component or essentially consists of a linear component. Along this linear component, the work piece and the at least one roller element move preferably at different velocities in the same direction.

Preferably, the at least one roller element and/or the at least one support element are moved additionally or alternatively in such a manner that the at least one support element and the at least one roller element perform a movement relative to each other, which comprises a linear component. Preferably, the relative movement between the at least one support element and the at least one roller element essentially comprises a linear component or essentially consists of a linear component. Along this linear component, the at least one support element and the at least one roller element preferably move in opposite directions.

In the method according to present invention for roll-solidifying the transition radiuses of crankshafts, the work piece arranged between the at least one support element and the at least one roller element performs a movement having a rotational component. According to a preferred embodiment, the work piece performs a movement having a rotational component and a linear component. According to the method according to the present invention, the at least one roller element and/or the at least one support element move along a path having a linear component and a rotational component wherein the linear component is preferably greater and particularly preferred substantially greater than the rotational component.

Preferably, the at least one roller element and/or the at last one support element do not rotate, particularly not around their own axis.

Furthermore, the present invention relates to a roller element for roll-solidifying the transition radiuses of crankshafts. Such a roller element is preferably suitable for or formed as roller element in the method according to the present invention for roll-solidifying the transition radiuses of crankshafts. The roller element according to the present invention comprises a substantially straight contact surface for introducing at least a roll-solidifying force into a crankshaft. For this purpose, the roller element has preferably an elongated shape, i.e., it extends in the direction of a longitudinal axis. Preferably, the substantially straight contact surface of the roller element extends in a longitudinal direction of the roller element, particularly preferably substantially parallel to the longitudinal axis of the roller element.

Preferably the substantially straight contact surface of the roller element has at least partially, preferably slightly, a concave and/or convex shape, namely in the plane in which the longitudinal axis of the roller element lies and which intersects the contact surface of the roller element, preferably essentially perpendicular.

Preferably, the contact surface of the roller element does not have a circular shape.

Preferably, the roller element or the contact surface of the roller element is not roller-shaped and/or is not formed rotation-symmetric.

The contact surface of the roller element has preferably a length of/between about 0.1 m up to/and 5 m, preferably of/between about 0.3 m up to/and about 2 m, particularly preferably of/between about 0.5 m up to/and about 1.5 m and more preferably of about 1 m.

Preferably the roller element according to the present invention comprises a contact surface having a roll-solidifying radius of/between about 0.5 mm up to/and about 5 mm, preferably of/between about 1 mm up to/and about 3 mm and particularly preferably from/between about 1.5 mm up to/and about 2 mm. Said roll-solidifying radius preferably lies in a plane which extends essentially about perpendicular to the longitudinal axis of the roller element as well as essentially about perpendicular to the contact surface of the roller element.

Furthermore, the present invention relates to an apparatus for roll-solidifying the transition radiuses of crankshafts according to the method according to the present invention. Further, the present invention relates to an apparatus for roll-solidifying the transition radiuses of crankshafts comprising a roller element according to the present invention.

An apparatus according to the present invention for roll-solidifying the transition radiuses of crankshafts comprises preferably at least one roller element for introducing at least one roll-solidifying force into the work piece as well as at least one support element for supporting the work piece against the force introduced by the roller element. Here, the at least one roller element and/or the at least one support element are preferably configured in such a manner that it comprises a substantially straight or linear contact area for introducing the at least one roll-solidifying force into the crankshaft or for supporting the work piece.

Preferably, the apparatus according to the present invention comprises means for generating a relative movement between the at least one roller element and the work piece, said relative movement having a linear component. Preferably the apparatus additionally comprises means for generating a relative movement between the at least one roller element and the at least one support element, said relative movement having a linear component.

For this purpose, the apparatus according to the present invention preferably comprises means which are adapted to generate such a relative movement essentially comprising a linear component or essentially consisting of a linear component. Furthermore, the apparatus according to the present invention preferably comprises means for relatively moving the at least one roller element and the at least one support element along a linear component.

The apparatus is preferably configured in such a manner that a work piece arranged between the at least one roller element and the at least one support element performs a movement having a rotational component. Furthermore, the apparatus according to the present invention is preferably configured in such a manner that a work piece arranged between the at least one roller element and the at least one support element performs a movement having a rotational component and a linear component.

The apparatus according to the present invention further preferably comprises means for moving the at least one roller element and/or the at least one support element along a path having a linear component and a rotational component, wherein the linear component is preferably greater and particularly preferred substantially greater than the rotational component. According to a preferred embodiment, the at least one roller element and/or the at least one support element cannot be rotated, particularly not around their own axis.

The present invention proves to be particularly advantageous in that it allows an optimized and reliable introduction of forces into the work piece. Furthermore, it preferably minimizes the risk of wear for both, tool and work piece. Additionally it preferably allows a variable introduction of forces into the work piece as well as a working also of complex work piece- and/or crankshaft geometries as, for example, crankshafts for V-engines with a narrow V-arrangement (for example, V-10 engine of Volkswagen). Additionally, the present invention preferably allows independent introduction and/or control of rolling forces of a single tool or roller element. Thus, preferably it is not only possible to achieve a variable or changing force over a working cycle but also an individual adaption of the force for each transition radius to be worked.

Furthermore, the facilitating of the machining of only one side, as for example, the working of only one side of a bearing seat independent from the other side of the bearing seat has preferably proven to be advantageous. Additionally, the working of narrower bearings is preferably facilitated by the present invention. The present invention preferably allows a good balancing or an optimized working of imprecisely milled transition radiuses.

It is preferably further advantageous that the roller element due to the straight configuration comprises a substantially longer contact surface from which each part comes only in contact with the work piece to a limited extent during operation. A damage of the tool is thus not or only insignificantly transferred to the work piece. Here, it is to be noted that a defect of the solidifying roller of 2/10 of the nominal size is assumed as threshold for a reliable working in roll-solidifying process in the state of the art. Greater defects lead to a material displacement on the work piece up to the standstill or blocking of the solidifying roller. This results in a unusable work piece and tool and requires extensive repairing and exchanging. Said disadvantages are preferably overcome by the present invention.

According to a preferred embodiment according to the present invention only one support element is used for each bearing seat, said support element is also configured according to the present invention as an elongated or linear support element and preferably has a width corresponding to the width of the crankshaft bearing. According to a further preferred embodiment, two rotation-symmetric or circular support elements are used for each bearing seat, said support elements being rotatably supported by a roller support head and preferably also having a width corresponding to the width of the bearing seat.

For achieving the relative movement between the roller element and the working piece preferably only the support element or the roller element moves. Preferably, the relative movement between the roller element and the work piece is effected only by a movement of the support element. Since the width of the bearing seat is increased by about 1/20 to about 1/10 by the force effective during the roll-solidifying process an angle change of the tool results. A respective adapting of the tool can be performed more precisely when the tool is stopped so that initiating of a movement by the support roll alone is advantageous. Particularly each bearing seat gets wider by about 0.05 mm to about 0.1 mm by the roll-solidifying. For a crankshaft for a four-cylinder engine, i.e. a crankshaft having 8 bearing seats, this results in a gain in width of about 0.4 mm to about 1 mm for the entire crankshaft.

As already described above, it is also possible to perform the roll-solidifying process in such a manner that the workpiece performs only a rotational movement, or that the work piece performs a combination of a rotational movement and a linear movement. Here, the machining comprising a linear movement of the work piece proves to be preferably advantageous in that the eccentricity of the crankshaft can be measured more precisely during working. This allows a real-time adjustment of the rolling forces in order to minimize eccentricity.

The present invention is described in connection with the roll-solidifying of the transition radiuses of crankshafts. It is obvious, however, that the invention is not limited to this application.

In the following, the present invention is described by means of preferred embodiments referring exemplarily to the attached Figures. Here, the following exemplary description, like the preceding one, relates to all subject-matters of the present invention, particularly the method according to the present invention, the apparatus according to the present invention as well as the roller element according to the present invention, to the same extent while it is not explicitly distinguished between them.

FIG. 1 shows a schematic view of a section of the top view of a roller element according to the present invention in an apparatus according to the present invention during rolling a bearing seat of a crank shaft;

FIG. 2 shows an enlarged view of a section of the top view of two roller elements according to the present invention during working of two transition radiuses of a journal of a crankshaft lying opposite to one another;

FIG. 3 shows a schematic view of a section of a side view of an apparatus according to the present invention with a tool according to the present invention as well as a support element during working of a crankshaft;

FIG. 4 shows a schematic view of a section of a side view of an apparatus according to the present invention having a tool according to the present invention as well as two support elements during working of a crankshaft;

FIG. 5 shows a side view of a preferred tool according to the present invention; and

FIG. 6 shows an enlarged schematic view of a section of a top view of a roller element according to the present invention during working of a crankshaft.

FIG. 1 shows a top view on two tools or roller elements 1 according to the present invention for solidifying surface layers and particularly for roll-solidifying preferably of crankshafts 2 or the transition radiuses 5 of journals 3 of crankshafts 2 (here only shown in section). In FIG. 1, two roller elements 1 are shown, namely for the working of a transition radius 5 _(L) shown on the left side in the Figure (roller element 1 _(L)) and for working a transition radius 5 _(R) shown on the right side in the Figure (roller element 1 _(R)). The crankshaft 2 comprises a journal 3 having a bearing seat 4 as well as transition radiuses 5 at the transition to the remaining part of the crankshaft 2, the transition radiuses being referred to as transition radius 5 _(L) for the left one in the Figure and transition radius 5 _(R) for the right one in the Figure, respectively.

Additionally, a support element 6 for supporting the work piece 2 against the roll-solidifying force introduced by the at least one roller element 1 is shown.

FIG. 3 shows a partial cross-sectional view along line A-A′ of the schematic view according to FIG. 1. FIG. 4 shows an alternative, preferred embodiment which essentially corresponds to the one shown in FIG. 3, wherein the support element 6 is formed by two roll-shaped support elements 9 which are arranged on a roll support head 10.

As shown, a roller element 1 according to the present invention comprises a contact surface 7 which is essentially straight. The contact surface 7 serves for introducing at least one roll-solidifying force into a work piece, here at a transition radius 5 into a crankshaft 2. The contact surface 7 preferably is essentially straight and extends further preferred essentially parallel to a longitudinal axis A of the roller element. During roll-solidifying of the transition radiuses of the crankshaft a relative movement is generated between the roller element 1 and the work piece, i.e., the crankshaft 2, wherein the crankshaft performs a rotational movement around its longitudinal axis B and rolls linearly on the essentially straight contact surface 7. Here, it preferably depends particularly on the relative movement between work piece 2 and roller element 1.

According to a preferred embodiment according to the present invention the roller element 1 performs a linear movement substantially in the direction of its longitudinal axis A wherein the work piece 2, i.e., the crankshaft 2 performs a circular or rotational movement along the longitudinal axis B.

Additionally, the crankshaft 2 also performs a linear movement in a direction parallel to the linear movement of roller element 1 in a preferred embodiment according to the present invention. According to a further preferred embodiment according to the present invention, the tool or roller element 1 stands still and only the work piece 2, i.e., the crankshaft 2, performs a rotational movement around its longitudinal axis B as well as linear movement along the contact surface 7 of the roller element 1.

Additionally, a support element 6 (see also FIG. 3) is shown which, according to a preferred embodiment according to the present invention, comprises a linear or straight contact or support surface 8. Preferably, the support element 6 has an essentially elongate shape and extends along a longitudinal axis C, wherein the support surface 8 is preferably formed essentially parallel to the longitudinal axis C of the support element 6. As can be taken from the top view in FIG. 1, the width of the support element 6 or the support surface 8 of support element 6 essentially corresponds to the width of the bearing seat 3 of the crankshaft 2.

In a roll-solidifying process according to a method according to the present invention the crankshaft 2 is supported by at least one support element 6 which absorbs the roll-solidifying forces introduced by the at least one roller element 1. For this purpose, the bearing surface 4 of the journal 3 of the crankshaft 2 abuts on the contact surface 8 of the support element 6.

During the roll-solidifying process, the support element 6 preferably performs a linear movement essentially along the longitudinal axis C (see also FIG. 3). According to a preferred embodiment of the present invention, the roller element 1 stands still during the roll-solidifying process, i.e., it does not perform a linear movement. Over support element 6 by means of its linear movement, preferably essentially along its longitudinal axis C or its contact surface 7, a rotational movement of crankshaft 2 is generated in such a manner that said crankshaft rolls on the roller element 1 which results also in a linear or longitudinal movement of crankshaft 2, wherein the transition radiuses 5 of journal 3 of crankshaft 2 roll on the contact surface(s) 7 of roller element(s) 7.

According to the preferred embodiment of the present invention shown in FIG. 4, roller element 1 performs a linear movement in its longitudinal direction by which a rotational movement of the journal 3 or the crankshaft 2 around its longitudinal axis is generated. The crankshaft or the bearing stud 3 in turn abut on two support roller elements 9 or their contact surfaces 20 which are provided on a roller support head 10. According to this embodiment according to the present invention, crankshaft 2 preferably does not perform a longitudinal movement. As described with regard to support element 6, support elements 9, too, preferably comprise a width corresponding to about the width of the journal 3. The support elements 9 are preferably supported rotatably around their axes D on a roller support head 10.

FIG. 2 shows an enlarged view of two roller elements 1 according to the present invention, which are referred to as left roller element 1 _(L) and right roller element 1 _(R) for a better distinction in the following. Said distinction, however, only relates to the arrangement of the roller elements in respect of the corresponding left and right transition radiuses 5 _(L), 5 _(R) of journal 3 of a crankshaft 2, from which the left transition radius in the drawing is referred to as 5 _(L) and the right one as 5 _(R).

According to exemplary, preferred embodiment according to FIG. 2, which essentially corresponds to the one shown in FIG. 1, shows a roller element 1 (here 1 _(L), 1 _(R)) according to the present invention comprising a substantially straight contact surface 7 for applying at least one roll-solidifying force on crankshaft 2. Here, the contact surface 7 is substantially straight, i.e., it essentially extends along the longitudinal axis A (here A_(L), A_(R)) of the roller element 1 (here 1 _(L), 1 _(R)).

In a top view according to FIG. 2, i.e., transverse to the longitudinal axis A or transverse to the straight extension of the contact surface 7, the profile of the contact surface 7 of a roller element 1 according to the present invention essentially complies with the geometric shape of the bearing seat 5 (here 5 _(L), 5 _(R)) or corresponds thereto. Here, it can preferably be reverted back to geometries known from the state of the art.

Preferably, the contact surface 7 of a roller element 1 according to the present invention comprises a radius which substantially corresponds to the transition radius of the journal of the crankshaft. According to a preferred embodiment, the radius of the contact surface 7 is equal to or smaller than the corresponding crankshaft radius. According to preferred embodiment, the radius R₇ of the contact surface 7 is in the range from/between about 0.5 mm up to/and about 5 mm, preferably from/between about 1 mm up to/and 3 mm and particularly preferred from/between about 1.5 mm up to/and about 2 mm. According to a specifically preferred embodiment of the invention the radius R₇ is about 1.5 mm for a transition radius R₅ of about 2 mm.

FIG. 6 shows an enlarged schematic view of a section of a top view of a roller element 1 according to the present invention in the area of the contact surface 7 during, prior to and after the working of a crankshaft 2 (see also FIGS. 1 and 2). The continuous line W₁ shows the position of the tool 1 and its contact surface 7, respectively, prior to the roll-solidifying. In the exemplary, preferred embodiment shown, the contact surface 7 comprises a radius R₇ of about 1.5 mm. The dotted line W₂ shows the position of the tool 1 or its contact surface 7 after the roll-solidifying. Also after the roll-solidifying, the contact surface 7 comprises a radius R₇ of about 1.5 mm.

The continuous line K represents the contour of the crankshaft 2 including the transition radius 5. In the exemplary, preferred embodiment, crankshaft 2 comprises a radius R₅ of about 2 mm in the area of the transition radius 5.

The exemplary diameter of bearing seat 4 prior to grinding thereof (if applicable prior to and after roll-solidifying) is referred to as diameter ØA in FIG. 6. The exemplary diameter of bearing seat 4 after grinding, i.e. the final size of bearing seat 4, is referred to as diameter ØE in FIG. 6. The two diameters ØA and ØE shown are exemplary extreme cases of the diameter of a bearing seat prior to or after grinding relating to the eccentricity of the bearing due to, for example, machining- and manufacturing tolerances. The maximum difference between diameter ØA prior to grinding and the diameter ØE after grinding is, for example, about 0.8 to 0.9 mm.

The distance p in FIG. 6 is the deformation of the transition radius 5 as a result of the roll-solidifying action. Thus, after roll-solidifying the contour, as shown as line K, of the crankshaft 2 is changed in the area of the transition radius 5 and essentially corresponds to the contour of contact surface 7 of tool 1 in the position after roll-solidifying as shown by line W₂. The distance p preferably lies in the range from/between about 0.05 mm up to/and about 0.5 mm and is preferably about 0.2 mm. As shown in FIG. 6, the angle α of the vector of the rolling force to the vertical on the bearing surface, which acts on workpiece 2 by roller element 1 via contact surface 7, is preferably 25° to 45°, particularly preferred 30° to 35°. This is preferably particularly advantageous in order to introduce internal compression tension of the first degree into the correct zone and/or in order to reduce internal compression tensions of the third degree in order to achieve a better crystal structure, in the direction of an ideal crystal structure.

As shown in FIG. 2, a tool according to the present invention comprises preferably two side areas of which the first side area 11 is directed to a shoulder 12 of the crankshaft 2. The second side area 13 lies on the side directed away from the shoulder 12 of the crankshaft 2, extending at the transition radius 5 to be worked. Preferably, the first side area 11 is recessed relative to the transition radius 5 or the contact surface area 7 in order to minimize the risk of collisions between the side area 11 and the shoulder 12 of the crankshaft.

According to a preferred embodiment, this is ensured by a lateral offset between the outer area 14 of the contact surface 7 and the side surface area 11, said lateral offset being achieved, for example, by forming the contact surface 7 in a protruding area 15 (cf. FIG. 2) and/or by tilting the side area 11 relative to the shoulder 12 of the crankshaft (cf. FIG. 1).

According to a preferred embodiment according to the present invention, the roller element comprises a second side area 13 which is formed to abut against a second roller element.

According to a preferred embodiment according to the present invention, the side surface area 13 comprises a substantially convex shape which forms an abutting area 16.

This allows an arrangement of two roller elements 1 _(L), 1 _(R) according to the invention as shown in FIG. 1 or FIG. 2. By providing two roller elements 1 _(L), 1 _(R) according to the present invention, it becomes possible to simultaneously work two opposite transition radiuses 5 of a bearing seat 3 of a crankshaft 2. The introducing of the rolling forces into the roller element 1 according to the present invention is performed at a force introduction area 17 by suitable means, said force introduction area is preferably provided essentially in the area of the roller element 1 lying opposite, relative to the longitudinal axis of roller element 1, of the contact area 7.

During the shown working or the shown simultaneous working of two transition radiuses 5 _(L), 5 _(R) the present invention allows the providing of two, preferably independent, roll-solidifying forces F_(L), F_(R) to be applied on roller element 1 _(L), 1 _(R), respectively. This preferably allows the precise adjustment of the required roll-solidifying force for the respective transition radius 5 _(L) or 5 _(R). This, in turn, allows an optimal adjustment of the roll-solidifying forces for each working case, as it can become necessary due to, for example, manufacturing inaccuracies during the preceding working of the transition radiuses. For this purpose, the forces F_(L) and F_(R) can preferably be adjusted independent from each other. The contact area 16 in the side area 13 of the roller element 1 according to the present invention is preferably formed in such a manner that it allows an automatic angle adjustment of the contact surface 7 relative to the transition radius 5. This preferably proves to be particularly advantageous in case of manufacturing inaccuracies of the crankshaft or when the distances of the transition radiuses 5 _(L), 5 _(R) to each other change during the roll-solidifying process.

Preferably, the shaping of the geometry of the cross-section of roller element 1 is dependent on the basic conditions of the single case wherein it is particularly essential to form a substantially straight contact surface. The cross-sectional shape of a preferred roller element (cf. FIGS. 1, 2) is essentially rectangular, triangular or oval.

As can be taken from the side view according to FIG. 5 of a tool or roller element 1 according to the present invention, the roller element 1 preferably comprises a substantially elongate shape and extends along a longitudinal axis A. The contact surface 7 of roller element 1 is preferably straight and preferably extends essentially parallel to the longitudinal axis A of tool 1. However, it is preferably only of importance that during the working of a transition radius of a crankshaft the contact surface 7 is in contact with the crankshaft in such a manner that the required roll-solidifying force F is introduced into the crankshaft. An apparatus according to the present invention for roll-solidifying of transition radiuses of crankshafts comprises suitable means or constructions for this purpose, said means effecting a respective guidance for and/or contact force of the roller element. According to a preferred embodiment according to the present invention the apparatus according to the present invention is adjusted in such a manner, or the method according to the present invention is performed in such a manner that the linear movement of the roller element 1 is essentially parallel to or in the direction of the direction of the contact surface 7.

As can be taken from the schematic drawing according to FIG. 5, in the side view of the roller element 1 the contact surface 7 of said roller element according to the present invention can have at least partially a concave and/or convex shape. This is indicated by the dotted lines 7′ and 7″ in FIG. 5. Preferably, the contact surface 7 of roller element 1 is not circular and not rotation-symmetric.

The contact surface of the roller element preferably comprises a length L from/between about 0.1 m up to/and 5 m, preferably from/between about 0.3 m up to/and about 2 m, preferably preferred from/between about 0.5 m up to/and about 1.5 m and particularly preferred of about 1 m.

The ratio of the length of contact surface 7 to the difference between the two extreme points of the contact surface related to the direction perpendicular or substantially perpendicular to the longitudinal axis A of the tool, here referred to as T, preferably goes to infinity particularly when the contact surface 7 has a straight shape. According to further preferred embodiments according to the present invention the ratio from L to T is in the range from/between about 4/1 and infinite, further preferred from/between about 8/1 up to/and 1000/1, further preferred from/between 20/1 up to/and 500/1, also preferred from/between 30/1 up to/and 100/1 and further preferred from/between about 50/1 up to/and 50/1.

Preferably a specifically long lifetime of the tool according to the present invention is achieved by the length L of the straight contact surface 7. Particularly, due to the rolling of the transition radius 5 to be worked on the contact surface 7 each part of the contact surface 7 comes into contact with he transition radius 5 only a limited number of times. The wear of the tool is correspondingly low. This results in a preferably elongated lifetime of the tool leading to a reduction of standstill times of the roll-solidifying apparatus due to, for example, change of tools and, thus, to time- and cost savings in the working of crankshafts. Furthermore, a damage at the transition radius 5 and/or the contact surface 7 comes in contact with the correspondingly counter surface, namely the contact surface 7 or the surface of the transition radius 5, only a limited number of times per working action, which leads to a reduction of the influence of a respective damage on the work piece and/or tool.

Preferably the working according to a method according to the present invention is performed by repeating or alternating linear relative movements between work piece and tool. Preferably a complete rolling movement of the tool over the work piece (back and forth) effects a rolling number of about 12 (the crankshaft rotates 12 times, i.e. performs 12 rotations, 6 times thereof per each travel of the tool, i.e., one back and forth movement) at a length of the tool or contact surface of about 1 m and the bearing seat of the crankshaft to be worked having a diameter of about 50 mm. As discussed above, the relative movement between the tool and the work piece can be generated by the tool itself and/or by the support element. Preferably, about 1 to 6 complete rolling movements between the tool and the work piece is/are required. A higher number of rolling movements per working action preferably results in a lower force required per movement which, in turn, results in an improvement of the roll-solidifying strength of the crankshaft to be worked. This is particularly advantageous for crankshafts to be used in diesel engines having a high torque. Preferably, two entire rolling movements relative between the tool and the work piece are performed. For crankshafts to be used in diesel engines, preferably about 3 to 4 complete rolling movements relative between work piece and tool are performed at a reduced roll-solidifying force. 

1. Method for roll-solidifying the transition radiuses of crankshafts comprising the steps of providing at least one roller element for introducing at least one force into the work piece; providing at least one support element for supporting the work piece against a force introduced by a roller element; moving the at least one roller element and/or the at least one support element in such a manner that the at least one support element and/or the at least one roller element perform a movement relative to each other and/or relative to a work piece, characterized in that said movement comprises a linear component.
 2. The method according to claim 1, wherein the relative movement between the at least one support element and the at least one roller element essentially comprises a linear component or essentially consists of a linear component.
 3. The method according to claim 1, wherein the at least one support element and the at least one roller element move in opposite directions along the linear component.
 4. The method according to claim 1, wherein the work piece arranged between the at least one support element and the at least one roller element performs a movement comprising a rotational component.
 5. The method according to claim 1, wherein the work piece arranged between the at least one support element and the at least one roller element performs a movement comprising a rotational component and a linear component.
 6. The method according to claim 1 comprising the step of moving the at least one roller element and/or the at least one support element along a path with a linear component and a rotational component, wherein the linear component is preferably greater and particularly preferred substantially greater than the rotational component.
 7. The method according to claim 1, wherein the at least one roller element and/or the at least one support element do not rotate around their own axis.
 8. A roller element for roll-solidifying the transition radiuses of crankshafts particularly according to claim 1, characterized in that said roller element comprises an essentially straight contact surface for introducing at least one roll-solidifying force into a crankshaft.
 9. The roller element according to claim 8, wherein the essentially straight contact surface of the roller element extends in a longitudinal direction of the roller element and has at least partially a concave and/or convex shape along said longitudinal direction.
 10. The roller element according to claim 8, wherein the contact surface of the roller element does not have a circular shape.
 11. The roller element according to claim 8, wherein the contact surface of the roller element has a length of about 0.1 m to about 5 m, preferably of about 0.3 m to about 2 m, particularly preferably of about 0.5 m to about 1.5 m and more preferably of about 1 m.
 12. The roller element according to claim 8, wherein the contact surface of the roller element comprises a radius for roll-solidifying of about 0.5 mm to about 5 mm, preferably of about 1 mm to about 3 mm and particularly preferably of about 1.5 mm to about 2 mm.
 13. A device having a roller element according to claim 8 for solidifying work pieces.
 14. A device for roll-solidifying the transition radiuses of crankshafts, particularly according to claim
 1. 15. A device for roll-solidifying the transition radiuses of crankshafts particularly according to claim 13 having at least one roller element for introducing at least one roll-solidifying force into the workpiece and at least one support element for supporting the work piece against the force introduced by the roller element, wherein the at least one roller element and/or the at least one support element is formed in a manner that it comprises an essentially straight contact surface for introducing the at least one roll-solidifying force into the crankshaft or for supporting the work piece.
 16. The device according to claim 13, wherein the device comprises means for generating a relative movement having a linear component between the at least one roller element and the work piece and/or the at least one support element.
 17. The device according to claim 13, wherein the device comprises means for generating a relative movement between the at least one roller element and the work piece and/or the at least one support element, the relative movement essentially comprising a linear component or essentially consisting of a linear component.
 18. The device according to claim 13, wherein the device comprises means for relatively moving the at least one roller element and the at least one support element in opposite directions along a linear component.
 19. The device according to claim 13, wherein the device is configured in such a manner that a work piece arranged between the at least one roller element and the at least one support element performs a movement comprising a rotational component.
 20. The device according to claim 13, wherein the device is configured in such a manner that a work piece arranged between the at least one roller element and the at least one support element performs a movement comprising a rotational component and a linear component.
 21. The device according to claim 14, wherein the device comprises means for moving the at least one roller element and/or the at least one support element along a path having a linear component and a rotational component wherein the linear component is preferably greater and particularly preferably substantially greater than the rotational component.
 22. The device according to claim 13, wherein the at least one roller element and/or the at least one support element cannot be rotated around their own axes. 